[LLVMdev] PrescheduleNodesWithMultipleUses() causing failure in PickNodeToScheduleBottomUp() ???

[Dan Gohman]

On Thu, Aug 22, 2013 at 4:15 AM, Robert Lytton <robert at xmos.com> wrote:

>
>
> Outstanding issues
> ============
>
> 1. Is it too aggressive in searching predecessors and successors?
>    Should the algorithm give up and assume the worst if the depth of
> search reaches a predefined limit?
>
> 2. Should the initial search for 'SetUp1' and 'Destroy1' only search along
> chains? viz conditional upon II->isCtrl()
>

The code is a kludge to work around a particular symptom of a deeper bug in
the underlying scheduling algorithm. It's entirely possible that you've
found a real bug in it; feel free to check in the fix if you're confident
it's right.


> 3. Is it possible to input a DAG for testing?
>

Only by constructing an LLVM IR testcase and feeding it all the way through.


>     What is the best way to construct the test case?
>

The above.


>     Using an IR as input does not guarantee the required DAG will be
> output for testing.
>

Yes, it is quite unfortunate.


>
> 4. Where should the test be placed?
>     (How do I test for no-assert?)
>

Just use an LLVM IR testcase which reproduces the problem before the fix is
applied.

Dan
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20130822/136fabf7/attachment.html>